partitioning

Partitioned table query still scanning all partitions

由 眉间皱痕 提交于 2019-12-05 08:12:41
I have a table with over a billion records. In order to improve performance, I partitioned it to 30 partitions. The most frequent queries have (id = ...) in their where clause, so I decided to partition the table on the id column. Basically, the partitions were created in this way: CREATE TABLE foo_0 (CHECK (id % 30 = 0)) INHERITS (foo); CREATE TABLE foo_1 (CHECK (id % 30 = 1)) INHERITS (foo); CREATE TABLE foo_2 (CHECK (id % 30 = 2)) INHERITS (foo); CREATE TABLE foo_3 (CHECK (id % 30 = 3)) INHERITS (foo); . . . I ran ANALYZE for the entire database and in particular, I made it collect extra

partition of a set or all possible subgroups of a list

由 耗尽温柔 提交于 2019-12-05 06:14:06
问题 Let's say I have a list of [1,2,3,4] I want to produce all subsets of this set which covers all members once, the result should has 15 lists which the order isn't important, instead t provides all possible subgroups: >>>>[[1,2,3,4]] [[1][2][3][4]] [[1,2],[3][4]] [[1,2],[3,4]] [[1][2],[3,4]] [[1,3],[2][4]] [[1,3],[2,4]] [[1][3],[2,4]] [[1],[2,3][4]] [[1,4],[2,3]] [[1][2,3,4]] [[2][1,3,4]] [[3][1,2,4]] [[4][1,2,3]] This is a set partitioning problem or partitions of a set which is discussed

Error using spark 'save' does not support bucketing right now

由 烂漫一生 提交于 2019-12-05 06:01:35
问题 I have a DataFrame which I am trying to partitionBy a column, sort it by that column and save in parquet format using the following command: df.write().format("parquet") .partitionBy("dynamic_col") .sortBy("dynamic_col") .save("test.parquet"); I get the following error: reason: User class threw exception: org.apache.spark.sql.AnalysisException: 'save' does not support bucketing right now; Is save(...) not allowed? Is only saveAsTable(...) allowed which saves the data to Hive? Any suggestions

Foreign keys vs partitioning

由 蓝咒 提交于 2019-12-05 04:41:21
Since foreign keys are not supported by partitioned mySQL databases for the moment, I would like to hear some pro's and con's for a read-heavy application that will handle around 1-400 000 rows per table. Unfortunately, I dont have enough experience yet in this area to make the conclusion by myself... Thanks a lot! References: How to handle foreign key while partitioning Partitioning mySQL tables that has foreign keys? Well, if you need partitioning for a table as small as 400.000 rows get another database than MySQL. Seriously. By modern standards any table below 1.000.000 rows is normally

How to partition a RDD

由 老子叫甜甜 提交于 2019-12-05 04:26:06
问题 I have a text file consisting of a large number of random floating values separated by spaces. I am loading this file into a RDD in scala. How does this RDD get partitioned? Also, is there any method to generate custom partitions such that all partitions have equal number of elements along with an index for each partition? val dRDD = sc.textFile("hdfs://master:54310/Data/input*") keyval=dRDD.map(x =>process(x.trim().split(' ').map(_.toDouble),query_norm,m,r)) Here I am loading multiple text

Dropping multiple partitions in Impala/Hive

由 ╄→гoц情女王★ 提交于 2019-12-05 04:03:54
问题 1- I'm trying to delete multiple partitions at once, but struggling to do it with either Impala or Hive. I tried the following query, with and without ' : ALTER TABLE cz_prd_corrti_st.s1mme_transstats_info DROP IF EXISTS PARTITION (pr_load_time='20170701000317') PARTITION (pr_load_time='20170701000831') The error I'm getting is as follow: AnalysisException: Syntax error in line 3: PARTITION (pr_load_time='20170701000831') ^ Encountered: PARTITION Expected: CACHED, LOCATION, PURGE, SET,

Understanding Dutch National flag Program

由 被刻印的时光 ゝ 提交于 2019-12-05 03:10:05
问题 I was reading the Dutch national flag problem, but couldn't understand what the low and high arguments are in the threeWayPartition function in the C++ implementation. If I assume them as min and max elements of the array to be sorted, then the if and else if statements doesn't makes any sense since (data[i] < low) and (data[i] > high) always returns zero. Where am I wrong? 回答1: low and high are the values you have defined to do the three-way partition i.e. to do a three-way partition you

How to detach a partition from a table and attach it to another in oracle?

由 こ雲淡風輕ζ 提交于 2019-12-05 02:06:47
问题 I have a table with huge data( say millions of records, its just a case study though!) of 5 years, with a partition for each year. Now i would want to retain the last 2 years data, and transfer the rest of the 3 year data to a new table called archive? What would be the Ideal method, with minimal down time and high performance? 回答1: alter table exchange partition is the answer. This command exange the segment of a partition with the segment of a table. It is at light speed because it does

How do I minimise the maximum aspect ratio of two subpolygons?

由 旧时模样 提交于 2019-12-04 23:59:47
问题 I'd like to cut a convex polygon into two with a given ratio of areas using a straight line, such that the larger aspect ratio of the two subpolygons is minimised. My approach at the moment involves choosing a random starting point, computing the appropriate end point that splits the polygon into the target areas, then calculating the larger of the two aspect ratios. Then repeating this lots of times until I'm close enough to a minimum! The aspect ratio of a polygon A is defined as: asp(A) :=

How does Round Robin partitioning in Spark work?

由 霸气de小男生 提交于 2019-12-04 19:45:15
I've trouble to understand Round Robin Partitioning in Spark. Consider the following exampl. I split a Seq of size 3 into 3 partitions: val df = Seq(0,1,2).toDF().repartition(3) df.explain == Physical Plan == Exchange RoundRobinPartitioning(3) +- LocalTableScan [value#42] Now if I inspect the partitions, I get: df .rdd .mapPartitionsWithIndex{case (i,rows) => Iterator((i,rows.size))} .toDF("partition_index","number_of_records") .show +---------------+-----------------+ |partition_index|number_of_records| +---------------+-----------------+ | 0| 0| | 1| 2| | 2| 1| +---------------+-------------
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